bits/pixels too low?

[capman21]

Ok fellows, I convert my dv file to xvid so I can keep it on my pc at a smaller size, but I was wondering what does this mean. Using GSPOT and looking at the original dv file the stats are Bitrate 28954, Fram Rate 29.97, and 2.795 bits/pixel. When I convert it to xvid I raise the bitrate and drop the fram rate to 25, and change the size from 720*480 to 702*480, but I notice my bits/pixel drop to 0.417. Question is wouldnt the quality be better if I was able to keep the bits/pixel around or close to 2.795?

[manono]

Hi-

Why 702x480? Isn't this a 1.33:1 video? And therefore shouldn't it be 640x480? I don't understand changing the framerate either, but maybe you have a good reason.

Of course, the higher the b/p*f the better the quality, but you'll never be able to reach the original 2.795. If you want good quality, you can do it for a constant quant 3 and check the b/p*f afterwards. If you want even better quality, possibly rivalling the source, do it for a constant quant 2, maybe turning off the B-Frames (or maybe not).

[capman21]

The original file is a 1:50:1 vid. I change the frame rate in hope of not having a lot of lag in the vid(slow pc). Ok, for what you were saying constant quant 3, etc can you use virtualdub to do all of this? Thanks for the info.

[guns1inger]

The original file, if DV, is 1.33:1. When converting to Xvid you have to take into account the fact that pixels aren't square on a TV, and have to adjust accrodingly. 640 x 480 is the 1:1 equivalent that you need to use for NTSC DV.

In fact, reading your two posts leads me to believe you have little to no idea what you are one about.

If you are having lag problems (filll in your profile so we know what hardware you have) then you should reduce the resolution and bitrate. If you screw with framerate you will introduce jerkiness that will be much worse than your lag.

The number you really need to worry about is kbps. If you drop the resolution down a bit, you can reduce the kbps substantially - to around 1200 for xvid, and still maintain quality. Your PC should be able to handle this.

[manono]

Ok, for what you were saying constant quant 3, etc can you use virtualdub to do all of this?

Yes, and faster than regular 2-pass encoding. Instead of choosing Target Bitrate in the first main XviD Config screen, click on it and then it will allow you to choose Target Quantizer.

guns1inger's tips are very good. If you really are having trouble with slow playback, lower the resolution. Changing the framerate not only won't help with playback, but is quite likely to mess things up in other ways, as he mentioned.

[capman21]

Did what you suggested and I was able to increase the bits/pixels from .417 to .858. Appreciate the advice.